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30 Cards in this Set
- Front
- Back
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CTD has a highly conserved amino acid sequence of Y_PT_PS.
How many times is it repeated in humans? In the yeast? |
YSPTSPS. 52x in humans, 26x in yeast
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Protein kinase phosphorylates the CTD. This marks the transition from initiation to _________.
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Elongation.
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In the YSPTSPS sequence two amino acids are phosphorylated. Which one, in what order and to what purpose. (Hint: 2 is 2nd)
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First: 5- serine to recruit capping enyzyme. Second: 2-serine recruits splicing protein.
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How do the phosphorylated serines recruit capping enzymes and splicing proteins? (What they "enchance"?)
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Enhance affinities and function of the enzyme or protein.
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Why must the mRNA be capped?
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To prevent digestion by exonucleases.
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Is CTD involved in poly adenylation?
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Yes.
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Is CTD involved in translation?
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No.
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The 5' cap is called a 7' methylguanylate CAP. The linkage is an unusual 5' - _', linked by three ________ bonds.
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5'-5'. Phosphodiester bonds.
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During the capping process in animal and higher plant cells, what happens to the first base?
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2' hydroxyl is methylated.
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In Vertebrates, where does methylation occur during capping?
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1st and 2nd bases on 2' hydroxyl.
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The pre-mRNA exits the transcription bubble after approximately __ nucleotides.
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25.
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To add the cap, which phosphate(s) do the capping enzyme remove? Another domain of the enzyme adds GMP _____.
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Enzyme removes gamma phosphate only. Separate domain adds GMP moiety to remaining 5' diphosphate.
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The transcripts of which RNA polymerases have caps? (Think about what the pols. transcribe.)
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RNA pol II only (only polymerase transcribing mRNAs)
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When hybridizing mRNA to DNA, why would the DNA loop out?
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Because there were no complementary mRNA regions for the introns of DNA.
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What are the two most highly conserved regions of introns? What do they contain?
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The borders. 5' end : GU. 3' end: AG.
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The branch point (Base is Adenine) is upstream of the _______-rich region, which is ~ 15 bases long.
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Pyrimidine rich region.
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How is the lariat formed?
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It's formed when the 2' hydroxyl of branch point attacks 5' phosphate group of first intron residue.
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In the first transesterification reaction, does the 2' hydroxyl group attack an intron or exon residue?
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5' intron residue.
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Describe how the molecules involved in second transesterification interact.
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The free 3' end of the first exon attacks the 5' phosphate of the following exon.
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Is ATP directly used for splicing or not? Explain.
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No it isn't. It's used to rearrange the spliceosome.
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Organize the following from slowest to fastest if run on acrylamide gel: Lariat, Lariat + exon, pre-mRNA, exons, debranched intron, 1 exon,
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pre-mRNA, Lariat+exon, Exons, 1 exon, lariat, debranched intron.
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Groups I & II introns are self-splicing; Which of the following belongs to which group? nuclear rRNA genes of protozoans.
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Group 1: nuclear rRNA genes of protozoans. Group 2: Some rRNA and tRNA genes in mitochondria/chloroplasts.
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What is the name of the ribonucleoprotein responsible for the majority of intron splicing? What are it's main components?
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Spliceosome. snRNA, and proteins, forming snRNPs.
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Categorize the snRNAs according to which RNA polymerase makes them.
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RNA polymerase II : U1, U2, U4, U5.
RNA polymerase I: U6. |
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Which snRNA interacts with the GU intron border?
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U1
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Where does the U2 snRNA interact with the intron?
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At the branch point.
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Why are mutations so dangerous to U1 function?
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The complementary sequence between intron and U1 is limited. Therefore any mutations will screw splicing up.
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Spliceosome formation: How do the snRNPs assemble on the intron; in what order? (Hint: some come as a trimeric complex.)
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U1 & U2 first. U4, U5, U6 come next as the trimeric complex.
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Rearrangements cause which two snRNPs to dissociate?
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U1 & U4
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Which two snRNPs are the 'catalytic core' of the spliceosome?
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U6 & U2
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